The invention concerns a device for controlling an electromechanical regulator provided in particular for controlling an internal combustion engine.
A known regulator (DE 195 26 683 A1) has an actuator designed as a gas shuttle valve and an actuating drive. The actuating drive has two electromagnets, between which an armature plate can be moved against the force of a return mechanism by switching off the coil current on the holding electromagnet and switching on the coil current on the capturing electromagnet. The coil current of the capturing electromagnet is kept constant by a preset capture value for a preset length of time and is then adjusted to a holding value by a two-position hysteresis controller.
Increasingly strict legal limits on the noise levels produced by a motor vehicle and demands for a quiet running internal combustion engine require that minimal noise be produced by the regulator for useful mass production. The regulator must also be guaranteed to be long lasting for useful mass production.
It is the task of this invention to create a device for controlling an electromechanical regulator which minimizes the noise produced when an armature plate contacts an electromagnet and also guarantees that the regulator will last a long time.
This problem is solved by the features of claim 1. Advantageous configurations of the invention are found in the subclaims.
In a coil through which a current flows and with which a moving plate of the armature is associated, there is, with an unsaturated magnetic circuit and a negligible stray flux, a clear connection between current I through the coil, the time differential of current dI/dt, air gap length l and velocity v of the armature. In the case of dominating magnetic resistance of the air gap to the remaining magnetic circuit, the following relationship can be found:                                           ⅆ            I                                ⅆ            t                          =                  -                      [                                                            2                  ⁢                                      xe2x80x83                                    ⁢                                      P                                          v                      ,                                              e                        ⁢                                                  xe2x80x83                                                ⁢                        1                                                                              ⁢                  l                                                                      AIN                    2                                    ⁢                                      μ                    o                                                              +                              Iv                l                                      ]                                              (G1)            
in which:
A is the bearing surface of the core of the electromagnet on which the armature plate is seated,
N is the number of windings in the coil,
Pv,el is the dissipated electrical power, and
xcexc0 is the air permeability.
The invention is based on the recognition that the first summand of relationship (G1) is negligible compared with the second summands of equation (G1) if the ratio of dissipated electrical power Pv,el and current I is low. The ratio of dissipated electrical power Pv,el and current I is almost zero when the coil is operated in the free-running operating state. Thus, in this case, the relationship                                           I            .                    I                =                  -                      v            l                                              (G2)            
results roughly from relationship (G1).
Thus gentle impact with v approximately zero can be achieved as a function of the time differential of current dI/dt and current I through the coil with air gap length 1 at zero without a position sensor having to be provided to detect the present position of the armature in each case. Long life is guaranteed since the regulator is only lightly mechanically stressed due to the soft impact of the armature plate on the core.
The control signals of the controller are determined with the coil in the free-running operating state. In the free-running operating state, the coil is short-circuited via a free-running circuit of the power regulator. In the free running state, the current I through the coil can be detected almost without loss. Thus the approximation of relationship (G1) given by relationship (G2) is highly accurate.
When there is a deviation from the desired relationship of the time differential of current dI/dt and current I through the coil in the free run, depending on the polarity sign of the deviation, electrical energy is preferably supplied to the actuator coil or removed from the actuator coil for a limited time. The free-running operation is stopped and the coil is applied to the distribution voltage (energy supply) or the stored energy is drained from the distribution voltage (energy drain).